Drivers are being warned the new 30km speed zones in the city come into effect from midnight.
It affects roads in residential and school areas between both canals.
The official launch was made at St Francis Street CBS on John Dillon Street this morning.
Roseann Brennan has been campaigning for the limits after her son Jake was knocked down and killed while out playing in 2014.
‘’I just heard this car and it was too late. It was the loudest bang you could hear in the world and I knew my life would never be the same again. My little boy flew up in the air and was dragged a few metres.
To all road users I want people to be aware that no one wants to live with regret in their lives due to a small mistake that could easily have been avoided.’’
There has been some criticism of the slower routes but road safety campaigners say it will save lives:
Councillor Ciarán Cuffe, Chairperson of Dublin City Council’s Transportation said “Lower speed limits mean safer streets and calmer communities. We're following the lead of cities like London and Edinburgh, and we're responding to the wishes of residents. Parents want their children to be able to walk and cycle and to school, and older people want to cross the road in safety. These measures will save lives".
You can check out the affected routes here: http://www.dublincity.ie/main-menu-services-roads-and-traffic-general-traffic-measures/speed-limits-your-area